Toxicity of snow cover for the assessment of air pollution as determined with microbiotests

Summary

Snow cover in the middle of Russia stays for up to 5 months per year, during which it accumulates various air pollutants. Snow contamination as such indirectly reflects the degree of air pollution and its distribution over a particular territory. A first attempt has been made to use microbiotests in complement to chemical analyses to evaluate the toxic hazard of the pollutants in the snow cover, which after melting will enter into surface and groundwaters. Bioassays were performed with the crustaceans Daphnia magna and Ceriodaphnia dubia, with the protozoan ciliate Parameciumcaudatum and with the bacterial ToxiChromotest. Snow samples have been taken in snow dumps of the City of Kazan from 1995 to 1997, and over the entire territory of the Republic of Tatarstan in 1998 in regions classified as having “ low ” or “ intermediate ” industrial emissions. Samples of road dirt were also collected in several streets of the City of Kazan for chemical and ecotoxicological investigations. The toxic effects found in the snow samples taken in 1995 and 1996, and the absence of toxicity in the snow samples taken in 1997 confirms the overall decrease of contamination of the snow cover revealed by the chemical analyses. The samples of road dirt in turn appeared to be seriously polluted with polycyclic aromatic carbons and were all acutely toxic to the crustacean D. magna. Toxic effects were also found in a number of the 87 snow samples collected in various regions of the Republic of Tatarstan, despite the rather low concentrations of the inorganic compounds analyzed. This points to the need of biotesting in complement to chemical investigations for a realistic evaluation of the hazard of air contaminants in snow.

Finally it also appeared from this preliminary study that the microbiotest with the ciliate protozoan P. caudatum was the least sensitive of the test species used and did not allow to detect toxic effects in any of the snow samples analyzed.